Vessel stabilizer



Aug. 20, 1968 J J. SLAGER ETAL 3,397,664

VESSEL STABILIZER 2 Sheets-Sheet 1 Filed Sept. 16, 1966 Fig.

11v VENTORS John J. S/ager William 61 Webster ATT%VEYS United StatesPatent 3,397,664 VESSEL STABILIZER John J. Slager, Silver Spring, andWilliam C. Webster, Glenelg, Md., assignors to Hydronautics, Inc.,Laurel, Md., a corporation of Maryland Filed Sept. 16, 1966, Ser. No.579,888 12 Claims. (Cl. 114-124) ABSTRACT OF THE DISCLOSURE A vesselstabilizer including a mass movable within a substantially gastight tubeand dividing it into left and right pressure chambers, resonant springtuning means normally maintaining the mass centered relative to thepressure chambers, the mass upon movement from center compressing thegas in the chamber in the direction of movement to establish a dampeningpressure resisting further movement of the mass.

The invention disclosed herein relates to a vessel stabilizer, and moreparticularly to a unitary self-contained, movable weighted massstabilizer.

It is recognized that both active and passive stabilize-rs are wellknown in the art. In recent years considerable development has beenpursued in passive type stabilizers, wherein fluid-containing wing tanksare interconnected by a cross-over conduit generally of a particularconfiguration to cause damping. The work of Frahm on passive stabilizersis well known. The Ripley patents disclose later developments. RipleyUS. Patent No. 3,083,671 discloses a passive wing-type system andinserts into the cross-over conduit '21 solid mass of greater densitythan the water which would otherwise remain in the crossover.

The development of active systems has not been extensively pursued inrecent years. This type of system requires control means, which must bevery sensitive to ship motion in order to rapidly activate themechanical anti-roll means. The control problems inherent in suchsystems, their cost and maintenance, led to the further development ofthe passive means.

The stabilizer disclosed herein may be considered passive, in that it isactivated by the application of an external force, namely the roll ofthe vessel. As the roll continues, the stabilizer will be inclined in anoscillatory manner, and the moving weight will oscillate. Associatedwith the weight are spring means tuned to cause resonant oscillation ofthe weight at or near the frequency of oscillation of the unstabilizedvessel. Also associated with the weight is a closed system pressureestablishing damping means to resist the weight movement and maintain itout of phase with the vessel oscillation. Herein both the tuning anddamping means are operably connected to and activated by movement of theweighted mass. Power driven electric, hydraulic, or other control meansare thereby eliminated.

The object of the invention is to provide a stabilizer of the abovedescribed type, having a minimum number of parts, which is entirelymechanical in operation, and which may be fabricated as a unitarystructure for installation aboard a vessel. The unit may be positionedon the main deck, where it will be readily available for adjustingpurposes and does not occupy valuable cargo or storage space. The changerequired in ship construction is the provision of additional structuralstrength which may be readily accomplished in new construction, as wellas in vessels in service, again without sacrificing space.

Another object is a stabilizer of small volume and weight, as comparedto passive liquid type stabilizers, making the stabilizer particularlysuitable for small craft "ice and vessels up to one thousand tonsdisplacement, wherein space is 'at a premium and added weightundesirable. For example, in a craft displacing approximatelysixty-seven tons, the weight of water required in a passive wing-typestabilizer would be approximately double that of the weight herein, andwith a movable rweight such as is disclosed herein, the space occupiedis approximately 10% of the volume require by water.

The foregoing and other objects and advantages will be apparent from thedescription herein when read in conjunction with accompanying drawings,wherein:

FIGURE 1 is a diagrammatic view of a vessel, partly in section, with thestabilizer mounted athwart the main deck;

FIGURE 2 is a perspective view of the stabilizer, partly in section;

FIGURE 3 is a plan view, also partly in section;

FIGURE 4 is a view taken on line 44 of FIGURE 3;

FIGURE 5 is a view taken 'along line 5-5 in FIG- URE 4;

FIGURE 6 is a view taken along line 66 in FIG- URE 4;

FIGURE 7 is a view similar to FIGURE 5 as modified, when the closedsystem pressure establishing means is wholly within the stabilizercasing.

As seen in FIGURES 1 and 2, the preferred embodiment of the stabilizer10 includes an elongated tube or casing 11 of rectangular cross-sectionand of substantial length relative to its width and height. Thestabilizer is positioned lengthwise athwart the main deck 12 of the hull14, and is secured to the deck by spaced depending foot members 16 andend brackets 20, which may be welded to the stabilizer and bolted to thedeck to permit removal of the stabilizer. The only installationrequirements are that the transverse center line of the stabilizer bealigned with the longitudinal center line of the vessel, and thestabilizer be rigidly secured to the vessel to roll therewith. Suitablestanchions 22 may be installed between decks to give additional support,if needed.

As the stabilizer 10 may be turned end for end, it will be described asviewed in the drawings rather with relation to its onboard installation.More particularly, the tube 11 is preferably made of suitable metal,having a top 26, front and rear side walls 28 and 30 and a bottom 36.Each end of tube 11 has an outer peripheral flange 31 to which left andright end closures 32 are respectively secured. For reasons hereinafterapparent, the tube is substantially gastight and has a smooth interiorsurface.

Movable vvithin the tube is a weighted mass 27 comprising an elongatedrectangular carrier 29 having front and rear 'side walls 37 and 38 (FIG.5) interconnected to left and right end walls 40 and 42. The end walls40 and 42 are also interconnected by a front partition wall 44, 'acenter partition wall 46. and a rear partition wall 48. Top and bottommembers 50 and 52 complete the carrier, and with the parallel partitionWalls define a pair of adjacent longitudinal compartments 54 and 56within. Carried on the bottom of each compartment is a lead weight 129of the compartment. The front compartment 54 (left as seen in FIGURE 5)has an opening 41 thereto through the carrier left end wall 40, and therear compartment 56 has an opening 43 thereto through the carrier rightend wall 42 (FIG. 2), the openings being above the weight, thecompartments being otherwise substantially gastight.

The carrier 29 is supported for movement on anti-friction devices hereshown as four rollers 60, one at each corner of the carrier. Each rolleris mounted on an axle 62 horizontally supported between the adjacentside and partition walls and so positioned that a small, peripheralportion extends through a slot in the carrier bottom and engages theinterior surface of tube bottom 36. Positioned above each roller is acentering caster 64, rotatable on a pin 68 vertically supported betweenthe arms of a U-bracket 70 Which'is secured to the adjacent partitionWall. The adjacent side walls are cut away to permit the casters toengage the adjacent interior wall surfaces of tube 11. The carrier 29and lead weights 129 make up the movable weight mass 27.

The carrier is approximately one-third the length of tube 11, anddivides the tube into leftand right-hand pressure chambers 72 and 74. Toestablish pressure within the chambers, the left and right end Walls 40and 42 of the carrier each have a sealing gasket 76 (FIGS. 4 and 6)secured around the outer periphery thereof, the-sealing gasket being inlight rubbing engagement with the interior surface of the tube, and thecarrier ends act as a piston upon movement of the carriage, to compressthe gas or air in the direction of movement, as more fully explainedhereinafter. A single seal could be used midway between the ends of thecarrier, but for convenience in manufacture, the end seals arepreferred.

When so constructed, when the weighted mass 27 moves upon inclination ofthe stabilizer by the roll of the vessel, themass will thereforeoscillate with the roll. As the oscillation must be at resonantfrequency, as explained above, there is associated with the mass 27,opposed left and right tuned spring damping means 78 and 80. The spring78 extends from the tube left closure member, to which its outer end issecured in any suitable way, and extends through the opening 41 incarrier left end wall 40, into the compartment 54, and has its inner endsecured to the carrier right end wall 42 (FIG. 3). The right-hand spring80 is similarly mounted, but in reverse manner, in that it extends fromright end tube closure member, extends through the opening 43 in thecarrier right end wall 42, into the compartment 56 and is secured to thecarrier left end wall 40. The axis of each spring is equidistant to eachside of the longitudinal center line of the tube, and in the samehorizontal plane.

The spring means 78 and 80 are spiral, have the same physicalcharacteristics, are tuned to the proper resonant frequency, are undercompression and exert equal and opposite forces on the mass 27 when thelatter is centered. The construction shown offers distinct advantages.By providing the carrier 29 with the longitudinally extending springreceiving compartments, the length of the spring is increased by thelength of the carrier compartment. In the embodiment shown, when thecarrier is centered, each spring is more than one-half the length of thestabilizer, thus permitting the use of long, light, sensitive springs.Additionally, as the mass 27 moves toward one end of the tube, as thespring is shortened, it, in effect, is swallowed within the compartmentallowing maximum movement of the mass.

As previously stated, the mass 27 divides the tube into left and rightpressure chambers, and as the tube is substantially gastight, movementof the mass operates the pressure establishing damping means. If themovement is to the right, the air or gas within chamber 74 will becompressed in the direction of movement and establish a pressure whichresists further movement of the weight. The air or gas in the leftchamber 72 is simultaneously expanding. Regulation of the damping may beaccomplished by bleeding air between the chambers thus reducing theresisting force in the direction of movement. This is accomplished byproviding a control means, comprising a tubular bypass 82 (FIG. 3)interconnecting the two pressure chambers. A throttle valve 94 isinstalled in the bypass 82, permitting regulation of the flow betweenchambers. The bypass openings into the chambers are each positionedabout one-half a carrier length from the end of tube, whereby thecarrier will close off the bypass opening in the direction of movement,and the remaining air will be rapidly compressed to establish a rapidrise in 4 pressure and provide addition-a1 resistance to cushion themass as it approaches the end of the tube. As the weight of the gas isinconsequential, the mass and springs constant, the variable is thechanging pressure force. By the use of air or other suitable gas,disturbance due to a sloshing of free water surface, is eliminated.

With the bypass throttle valve 94' exterior of the stabilizer, thedamping may be readily adjusted. The ready rapid adjustment is highlydesirable as1it allows operation at maximum effectiveness over a rangeof metacentric heights. For instance, after discharge of cargo, thestabilizer may be quickly tuned'to the changed ship condition. I

s As there are occasions when it maybe necessary to move the mass withinthe tube without inclining the ves sel, means are provided for moving itmanually and means to lock it in a set position. These means include acable 90 which'is attached to the left front wall 40 of the carrieradjacent the inner side wall of the tube 11, it then parallels thetubing front wall 28 to a horizontally arranged sheave 92' rotatable ona vertical pin 95, positioned in a box casing 96 projecting outwardlyfrom the front wall of the tube 11. Cable 90 makes a reverse turn aroundthe sheave 92 and exits from the casing through a suitable packinggland, then runs parallel to the exterior of the tube and enters a boxcasing 96 at the right end of tube, again making a reverse turn around asheave 92, and parallels the inner wall of the tube and is connected tothe right end wall 42 of the carrier. The exterior run of the cable maybe marked to show the interior position of the mass, as by a slacktake-up turn buckle positioned to show when the mass is centered. Thecable 90 may be secured in position by clamping the cable betweenmembers 97 and 98, one of which may be operated by a screw jack 100,diagrammatically shown, as any suitable type will do. A power drivemeans could be associated with the cable 90 for moving it, but it isapparent that a seaman could take a purchase thereon and utilize a blockand tackle to accomplish the result.

Numerous other refinements may be made. For example, the interior endsof tube 11 may be covered with a cushioning material 102 to act as ashock absorber, should a spring break. Also, to protect the bypass 82and cable 90, a hinged cover 104 is provided, the cover having asuitable slot therein through which the throttle valve 94 stem projects,permitting access to it at all times.

It is apparent that the tube 11 could be circular in crosssection; andthe mass could be cylindrical, with oppositely disposed open endchambers to receive the springs. The interior surfaces of the tube andexterior surface of the weight may be highly polished, coated withsuitable lubricating substances or provided with radially disposedrollers or other means, to permit ready movement. From a practicalstandpoint, the high cost involved, gives preference to the embodimentshereon.

For small craft, where little change in draft occurs between light andheavy conditions, the exterior bypass 82 between the pressure chambers72 and 74 may be eliminated, and one or both of the carrier compartments54, 56, may have an opening 106 in the end wall opposite the springentrance opening (FIG. 7), through which air may pass, whereby thepressure build-up to one side of the mass is controlled by the constantrelease of air to the other. This simplifies the structure, for smallcraft wherein displacement is relatively constant. Minor air or gasleakage either from the tube or past the carrier does not adverselyaffect the operation.

From the foregoing, it will be seen that the mass is the motivatingforce and becomes operable upon inclusion of the stabilizer. The springresonant tuning means are operably connected between the stabilizercasing and the mass and are activated upon movement of the mass. Thepressure establishing means become activated upon the movement of themass and the pressure established is the variable force in that the massand spring means are constant. Pressure adjustment is accomplished by asingle throttle valve in the pressure establishing means.

The stabilizer having been described, the patentable subject matter isset forth in the following claims.

We claim:

1. A unitary self-contained vessel stabilizer including:

(a) an elongated closed airtight tube;

(b) a weighted mass of lesser length than the tube movablelongitudinally of the tube;

(0) resonant spring tuning means operably connected between the mass andthe tube and applying equal and opposite forces on the mass when themass is centered in the tube and activated by movement of the mass; and

((1) pressure establishing means associated with the weighted mass andoperably responsive to the mass upon movement thereof to compress theair in the direction of movement to establish pressure dampening themovement of the mass as the latter moves i from center.

2,. The stabilizer defined in claim 1 including bleeder control meansfor adjusting the pressure established by the pressure establishingdamping means.

3. The stabilizer defined in claim 1 wherein the tube is rectangular incross-section, and including an elongated rectangular weighted movablecarrier, and said resonant spring tuning means comprises a pair ofsprings, one connected between one end of the tube and one end of thecarrier, and the other connected between the other end of the tube andthe other end of the carrier.

4. The stabilizer defined in claim 3 wherein each spring extends intothe carrier and connects to the end of the carrier remote from the endof the tube to which it is connected.

5. The stabilizer defined in claim 3 wherein the carrier includessealing means dividing the tube into left and right dashpots, said meanscompressing the air in the direction of movement of the carrier toestablish pressure resisting the movement of the carrier.

6. The stabilizer defined in claim 5 including a bypass between thedashpots.

7. The stabilizer defined in claim 6 wherein the bypass is an openingthrough the carrier.

8. The stabilizer defined in claim 6 wherein the bypass is a conduitexterior of the tube and having its ends respectively opening into theopposite dashpots, and a throttle valve in the conduit.

9. The stabilizerdefined in claim 3 including means connected to thecarrier and extending exterior of the tube for manually moving thecarrier.

10. The stabilizer defined in claim 9 including means for securing saidlast named means.

11. The stabilizer defined in claim 2 wherein said bleeder means isclosed by the weighted mass after predetermined movement of the mass.

12. A vessel stabilizer including (a) left and right gastight pressurechambers;

(b) a weighted means movable in said chambers to compress the gas in thechamber in the direction of movement of the mass whereupon the gas inthe other chamber may expand;

(c) bleeder means interconnecting the chambers to control the pressuretherebetween;

(d) and resonant spring tuning means normally acting to maintain theweighed mass centrally of the chambers.

References Cited UNITED STATES PATENTS 1,853,069 4/1932 Minorsky 114-1243,083,671 4/1963 Ripley 114-124 MILTON BUCHLER, Primary Examiner.

TRYGVE M. BLIX, Assistant Examiner.

